Secrecy and motor control device



April 8, 1941.

. A. SPENCER SECRECY AND MOTOR CONTROL DEVICE Filed Nov. 23, 1938 2Sheets-Sheet l p 8, 1941' J. A. SPENCER A 2.237.533

SEGRECY AND MOTOR CONTROL DEVICE F1 led Nov. 23, 1938 2 Sheets-Sheet 2Riff/Vii INVENTOR h JZH. JP/VC 1? BY v I MWL/ ATTORNEY Patented Apr. 8,1941 2,237,533 SECRECY AND MOTOR CONTROL DEVICE James A. Spencer,Teaneck, N. J., assignor to Radio Corporation of America, a corporationof Delaware Application November 23, 1938, Serial No. 241,942

14 Claims.

This invention relates to telegraph systems either wire or radio.Telegraph messages when radiated into the air in accordance with thecode sent out by an automatic transmitting head can be picked up by areceiver and interpreted by any one familiar with the code. In wiretelegraphy messages likewise can be surreptitiously received andinterpreted by tapping the wire over which the message is sent. It istherefore desirable to break up the message into unintelligiblecombinations so that unauthorized persons cannot interpret the messages,

It is an object of this invention to so change the communication signalssent over the air, or a conducting wire, that the message isunintelligible until it is transformed back into its original condition.

More specifically, it is an object of the invention to periodicallyreverse in accordance with a predetermined plan, the signal currentsbeing transmitted and-received.

Other objects will appear in the following description, reference beinghad to the drawings, in which:

Fig. 1 is a diagrammatic illustration of the transmitting circuit.

Fig. 2 is a diagrammatic illustration of the receiving circuit.

Fig. 3 shows graphs of the signals in my improved system.

Referring to Fig. 1, CR indicates generally a series of relays arrangedto operate in succession to serve as a counting device for reversing thetransmitted current after a predetermined time. I indicates thetransmitting relay operated by the automatic transmitterdiagrammatically indicated at 2. This automatic tape transmitter isoperated at a given constant speed to alternately elevate two plungersagainst a tape. having a series of spaced holes previously punched inaccordance with the message that is to be transmitted. Since this typeof tape transmitter is well known in the art the action is simulated inthe diagrammatic illustration by a pivoted lever 3 moving about itscenter point to alternately engage contacts 8 and 5., whenever theperforations in the tape permit the contact to be made.

The relay I is polarized so that current through coil 5 and 1 moves thetongue in opposite directions to open and close the switch.

The switch tongue in relay 9 in one position engages the positiveterminal l0 and in the other position the negative terminal ll. Relay 9is a modified Gulstad relay that differs from the standard Gulstad relaychiefly in having a holding coil l2 that prevents the tongue l3 fromvibrating at keying frequency while it is energized. When the coil i2 isdeenergized the tongue l3 can then move in response to the impulses ofcoils l3 and I4. I

Current for the coils l3 and I4 is supplied from the contacts 10 and IIthrough conductor I5. The coils are grounded at 16.

Reference character I! indicates generally a frequency control relaythat is also of the Gulstad typeexcept that additional coils l8 suppliedfrom the transmitting relay 1 correct the relay for any minute variationin frequency and phase by pulling the switch tongue into step with theimpulses sent out by the transmitting relay l. The method of operationof the relay I1 is as follows:

With the switch tongue 49 in engagement with the positivemarking contact20, current passes through conductor 2| to coil 22 through a suitableresistance 23, coil 24, to ground and back to the mid terminal of thebattery 26. At the same time current from conductor 2i passes throughcoil 21 to the condenser 28, resistance 29, to ground and to theintermediate terminal of the battery 26. The coils 22 and 21 act inopposition at this time so that while coil 22 tends to force the switchtongue away from contact 20, coil 21 tends to hold it against thecontact 20. The magnetic pull of coil 21 predominates at first becauseof the rush of current through condenser- 28. This charging current,'ofcourse. diminishes with time while the current through coil 22 builds upwith time because of the inductance in the circuit. When the currentthrough coil 21 stops or is sufficiently reduced, coil 22 predominatesand pulls the switch tongue l9 towards contact 25. As soon as the switchtongue leaves contact 20 the circuit is interrupted and the condenser 28instantly discharges through coil 21 in the reverse direction passingalso through coil 22 and the resistances 23 and 29. This flow ofcurrent, it will be noted, is in the direction to move the switch tongue[9 over against the contact 25 which it engages before the current diesdown.

The currents through coils 22 and 21 are reversed when contact is madewith terminal 25 because this is the negative terminal of the battery.With this reverse of current, coil 21 holds the tongue ill in engagementwith terminal 25 while the condenser 28 is charging, and coil 22attempts to open the contact but at first coil 21 predominates. When thecondenser 28 is charged or reaches a certain stage of charge, therepelthe marking contact 3|.

lent force of coil 22 predominates and the switch tongue I9 is thrusttoward the contact 29 and this action is aided, as before, by thedischarge current of the condenser through the coils.

The relay i'l thus oscillates a:- a predetermined frequency dependingupon the capacity of the condenser, the inductance of the coils, thevalue of the resistances and the potential of the battery. By proper;adjustment any desired frequency of vibration may be produced. This willbe practically constant though there would be a tendency to varyslightly in frequency or in phase. The coil i8, however, will delay orspeed up the action suificiently to hold the relay in step with thekeying speed of the automatic tape transmitter 2.

The relay 9 also is adjusted so that it tends to oscillate in step withthe keying speed of the transmitter 2 in exactly the same way as relayl1 but the tongue can move only when coil i2 is deenergized. This isdeenergized only at the end of the operation of the bank of timing orcountmarking and spacing contacts 3| and 32. These contacts eachalternatelyv energize one-half of the bank of timing or counting coilsCR in succession, one-half through conductor 33 and the other throughconductor 34. The transmitter relays are not polarized so the reversedand unreversed current operate the coils in the same way. The operationof the transmitting system will now be explained.

It will be assumed that tongue I3 is in engagement with contact 10 whenkey lever 3 engages contact 4. Switch 3513 closed at this time and coill2 energized. This puts positive current through coil 3 which throws thetransmitting relay tongue 35 into engagement with the positive contact31. This will send out a pulse in accordance with the signal through'thetransmitting apparatus indicated by the tone keyer 33 and radiotransmiter 33. This is marking current as tongue I! is in engagementwith the marking contact 20.

When the lever 3 of tape transmitter 2 ena es contact 5 the polarizedrelay tongue 36 will be thrown against the blank contact 40 and nocurrent will be sent out through the radio transmitter. Positive pulsesare thus being used by the tape transmitter for marking and negative forspacing, but this is reversed periodically by the counting relays CR,the operation of which will now be referred to in detail.

As soon as the marking contact was made with contact 20. as firstreferred to, coil 24 of relay I! threw switch tongue 30 into engagementwith Current from contact H) of relay 9 and conductor 4| then passedthrough switch contact 3| to conductor 33, conductor 42, coil 43 ofrelay I, conductor 44 and back-switch 44 of relay VIII to ground. RelayI was thus energized when the first marking contact was made in relayIT. The operation of relay I closes switch 45 and coil II is energizedwhen the relay tongue swings on to spacing contact 32. This energizationis produced by current flowing through conductor 34, the coil. Of

relay II, switch 45, conductor 44 and switch 44' to ground. Relay IIoperates and closes switch 41.

It should be explained at this time that relays I and II, as well aseach of the other counting relays, are held energized by holding coils,the circuit of which is closed at 49 by the operation of. a precedingrelay.

It will not be necessaiy to trace the circuit of the remaining coils ofthe counting relays as it will be seen that these relays are energizedprogressively by the vibrating tongue 30 and switches 41, 50, 60,13, Hand 18.

The energizing and holding currents oi. the timing relays pass throughthe contact 44'. Therefore, when relay VIII is energized the circuits ofall the timing relays are open by operation of this switch. This at oncedeenergizes all of them and this immediately reclcses switches 35 and44'. The time taken to energize the series 01' relays may be madeanything desired. While the series of relays RC were being energized thetransmitter was sending out positive current for marking.

Just as soon as switch 35 opens, coil [2 is deenergized momentarily andthis happens while the switch tongue 30 is starting towards spacecontact 32. Therefore, switch tongue i3, being new free to move, swingsinto engagement with its spacing contact I i. However, switch tongue I3is forced to remain against contact II by the immediate re-energizationof coil l2 by reclosure of switch 35.

The timing relays I to VIII are again energized progressively and duringthis period negative current is sent into the coils 8 and 1 oftransmitting relay I. This means. of course, that the current will bereversed in these coils. Whenever a marking pulse is sent out by thetape transmitter 2 the relay tongue 33 will be thrown against deadcontact 43 and when a spacing pulse is sent out relay tongue 35 will bethrown against the marking contact 31. This sends current to the antennafor the spaces of the signal.

In the embodiment shown the reversal of mark and space indications takesplace every four dotcycles and the effect is shown in Fig. 3 where graphA represents a normal signal for the word "and." Graph B represents thesame signal sent out by my improvement. with reversals taking placeevery four dot cycles. From a to b unreversed signals are transmitted.From I) to c the signals are reversed. At the point e the signals areagain normal and so on. The signal radiated by the antenna is indicatedby graph C.

"The receiver of Fig. 2 is arranged with a series of counting relays CR.a frequency control relay II, a transfer relay 9 and line relaygenerally indicated at 3|, that are the same or practically the same asthe similar relays'in the transmitting end of the system.

The vibrations of the relay I1 are maintained in exact phase andsynchronism with the transmitter by the pulses received through thereceiving apparatus 32, 33, line 84, condenser 35 to coil l3. The switchtongue of the transfer relay 9 is prevented from continually oscillatingby the holding coil i2 energized through back contacts 44 of the relayVIII. Parts in the receiving circuit of Fig. 2 that are similar to thoseof the transmitting system of Fig. 1 have in general similar referencecharacters.

In the receiving circuit, the polarized line relay consists of coils 33and 33 which when energized move the switch tongue in oppositedirections. Coil 88 predominates over coil 89.

When the rectified signal D is received, the current pulses passing overline 84 will cause switch tongue 9% to engage contact 9|. At this timetongue I3 is held against the positive contact and positive current willtraverse coil 92 of the polarized recorder. Stylus 94 will be attractedtoward coil 92. The moving tape 95 will then receive a mark" record..then no current is being received over line 84 in the spaces of thesignal the battery coil 89 throws the switch tongue 90 into engagementwith contact 95. This energizes coil 93 which attracts stylus 94 intoits spacing position. The recorder will record the signal at this timeas given between the points a and b of graph E. 1

When reversed signals between D and c of graph D are being received overline 84, switch tongue 90 will be moved against contact SI for thespaces. At the point b of graph D the counting or timing relays CR havejust completed their operation and the momentary interruption of currentthrough coil [2 by the opening of switch 44' permitted tongue I3 to moveagainst the negative terminal where it was held by the immediatere-energization of this coil. Therefore, at point b negative currentcommences to operate the recorder. This current passes from contact 9ithrough coil 92. The stylus is thrown away from the coil since thecurrent is now reversed. A space will thus beformed. When the currentceases to flow in the line 84 at the termination or" the space. coil 89throws the tongue against contact 95. This puts negative current throughcoil 93 and stylus 94 is repelled toward coil 92. This produces a "mark"record. Thus, the signals reversed at the transmitter are again reversedat the recorder and normal signals are produced as in graph E.

When the transmission of signals is interrupted for a substantial lengthof time there will be no current at the receiving end in coil 18 ofrelay I! to cause the timing relays to operate in exact phase andsynchronism with the timing relays at the transmitter. To prevent thetransmitting and receiving relays from getting out of step duringinterruptions, I provide slow release relays 97 which will not operateduring the short spacing intervals between the code characters but whichwill operate when the transmission and reception ceases. When the slowrelease relays operate, the circuits of the locking coils l2 and theholding coils of the counting relays are opened by de-energization ofcoils 98. While the transfer relay and the counting relays at thetransmitter and receiver still vibrate, the counting relays areinoperative until signal current again energizes the slow releaserelays. When this happens the coils l8 pull the receiving relays 9 andi! into step with the transmitting relays. The counting relays at thetransmitter and receiver thus start in synchronism.

While I have described my invention in connectlon with a simplex system,it will be apparent t that it can be used equally as well in multiplexsystems. for example, such as shown in Mathes Patent No. 1,979,484,November 6, 1934, and when so used the relays l1 and 19 can be used tocontrol the distributors. as they are vibrating in synchronism and phasewith the keying speed.

I have shown eight timing relays but any number from two on up may beused equally as well. Various other modifications may be used withoutdeparting from the spirit of the invention.

, Having described my invention, what I claim is:

1. In a secrecy telegraph system, means for making mark and spaceindications for transmitting a message and means for automaticallyinterchanging the mark and space indications at predetermined intervals.

2. In a secrecy telegraph system, means for making mark indications bycurrent of one character and a space by current of another character andmeans to automatically interchange the application of said currents forinterchanging the mark and space indications.

3. In a secrecy telegraph system, means for making mark and spaceindications by pulses of different signs and means for reversing thesign of said pulses for automatically interchanging the mark and spaceindications after predetermined intervals.

4. In a secrecy telegraph system, for reception of signals having markand space indications periodically interchanged, means for receiving theindications and means for automatically interchanging the mark and spaceindications at said predetermined intervals.

5. In a secrecy telegraph system, a transmitter switch, means to operatesaid switch for sending current of one character for markingindications, and a timing mechanism acting at predetermined intervalsfor automatically causing said means to operate said switch for sendingcurrent of the same character for space indications.

6. In a secrecy telegraph system, a source of current supply, a polarswitch having mark and space positions, two coils for operating saidswitch, a keying device for sending current through one of said coilsfor moving the switch to one position and through the other for movingit to the other position, and timing means acting at predeterminedintervals for alternately connecting said keying device to the positiveand negative terminals of said supply.

7. In a secrecy telegraph system, a sending station, a code transmitterat said station for making mark and space indications, means at saidstation for automatically interchanging the mark and space indicationsof the code transmitter at predetermined intervals, a receiving stationand means at the receiving station for automatically interchanging themark and space indications in synchronism with the first mentionedmeans.

8. In a secrecy telegraph system, a sending station, a code transmitterat said station for making mark and space indications, means at saidstation for automatically interchanging the mark and 'space indicationsof the code transmitter at predetermined intervals, a receiving station,a recorder at-the receiving station and means at the receiving stationfor automatically causing the recorder to interchange the mark and spaceindications in synchronism with the changes made by the first mentionedmeans.

9. In a secrecy telegraph system, a sending station, a code transmitterat said station for making mark and space indications, a timingmechanism at said station for automatically interchanging the mark andspace indications of -the code transmitter at predetermined intervals,

a receiving station, timing mechanism at the receiving station forautomatically interchanging the mark and space indications in syn- 10.In a secrecy telegraph system, a sending station, a code transmitter atsaid station for making current variations indicating marks and spaces,a receiving station, means at the sending station for automaticallyinterchanging the current variations to send space variations for marksand mark variations for spaces and means at the receiving station forautomatically altering'the' recording means to thereupon record marksfor spaces and spaces for marks.

'11; In a secrecy telegraph system, a polar relay for making mark andspace indications, a source of voltage, a reversing switch, a codetransmitter for applying energizing voltage to said relay from saidsource through said switch, a vibrator operating at constant frequencyapplying force tending to cause the switch to operate at a constantfrequency, means for preventing the vibrator from operating said switchand means operating at predetermined intervals for neutralizing theaction of the first mentioned means to permit the vibrator to operatethe reversing switch.

12. In a secrecy telegraph system. a polar relay for making mark andspace indications, a source of voltage, a reversing switch, a codetransmitter for applying energizing voltage to said relay from saidsource through said switch, a vibrator operating at constant frequencyapplying 13. In a secrecy telegraph system for reception of signalshaving marks and spaces periodically interchanged at the transmitter, areceiver. electromagnetic means connected to the receiver for makingalternate mark and space indications when voltage of one sign is appliedthereto and for reversing said indications when voltage of opposite signis applied thereto, a reversing switch, a source of voltage supplyconnected to said means through said switch and means for operating saidreversing switch when the marks and spaces in the receiver are reversed.

14. In a secrecy telegraph system, a polar relay for making mark andspace indications, a source oi voltage, a reversing switch, atransmitter for applying energizing voltage to said relay from saidsource through. said reversing switch, a vibrator operating at aconstant frequency tending to cause said switch to reverse at saidfrequency the operating voltage applied to the relay, .a magnet whenenergized preventing said vibrator from operating said switch and meansoperating at predetermined intervals for tie-energizing said magnet fora half cycle of the frequency of said vibrator to permit it to operatesaid reversing switch, a recorder having electromagnetic means formaking marks and spaces when voltage of one sign is applied thereto andfor reversing the marks and spaces when voltage of opposite sign isapplied thereto and means at the receiver for reversing the voltageapplied to the electromagnetic means when the reversing switch at thetransmitter is operated.

J AIVIES A. SPENCER.

